1. Field of the Invention
This invention relates to a display corrector and, more particularly, to a corrector to be used within a flat faced cathode ray tube display and which compensates for vertical and horizontal positional distortion and defocusing of points contained thereon.
2. Discussion
Flat faced cathode ray tube (CRT) displays are used in a wide variety of electronic applications requiring high accuracy and minimal display errors, such as in airplane displays. While these flat faced displays provide high accuracy, their geometrically flat face causes significant variation in deflection sensitivity and spot size relative to points appearing thereon. This sensitivity variation causes both horizontal and vertical positional distortion or displacement of the displayed points relative to their position upon an ideally spherically shaped display. The spot size variation causes these points to be defocused or blurred upon the display. These difficulties are well known in the art and are commonly referred to as "pin-cushion" distortion and defocusing, and are particularly obvious and troublesome at the turned edges of the flat faced display.
One approach to correcting these difficulties has utilized an electronic corrector embodying a square root approximation of the horizontal and vertical spherical positional error associated with the displayed points. This approach has only proven to alleviate a portion of the total distortion and defocusing while utilizing a complex electronic network which has proven to be relatively costly and subject to error.